In recent years, HEMTs (High Electron Mobility Field Effect Transistors) have found wider use in low loss high frequency and low loss high power applications. Gallium nitride (GaN) based HEMT-devices have been found to be particularly well suited for use in DC rectifiers, power microwave and radar amplifiers, low noise amplifiers, and high temperature elements, etc. Gallium nitride (GaN) material shows a high polarization effect, including spontaneous polarization and piezoelectric polarization. Even without being doped, this polarization effect allows forming a two-dimensional-electron gas (2DEG) adjacent to an interface (heterojunction) of a GaN/AlGaN (gallium nitride/aluminum gallium nitride) heterojunction structure (or GaN/AlInGaN, AlGaN/AlInGaN, aluminum indium gallium nitride). In a 2DEG, the electron concentration is related to the intensity of polarization. 2DEG sheet electron concentration of GaN/AlGaN heterojunction structures can reach very high values. Therefore, field-effect-transistors based on GaN/AlGaN heterojunction structures are able to control very large current.
Due to the ongoing developments of further shrinking, small chip carriers (small packages) such as SMD packages (surface-mount device) for III-nitride devices, in particular III-nitride devices formed by heteroepitaxy such as GaN-on-Si (gallium nitride on silicon) devices, are desired that allow dissipation of high power densities in small volumes during operation and/or fulfill standardized reliability tests such as the HTRB (high temperature reverse bias) test.